Oil circuit breaker having groups of contacts arranged opposite each other on an insulator and having helical creep-preventing ribs



INVENTOR.

April 19, 1966 H. FORWALD OIL CIRCUIT BREAKER HAVING GROUPS OF CONTACTS ARRANGED OPPOSITE EACH OTHER ON AN INSULATOR AND HAVING HELICAL CREEP'PREVENTING RIBS Filed 001;. 21, 1963 f/AA/( PaPwnLp BY Q United States Patent OIL CIRCUIT BREAKER HAVING GROUPS OF CONTACTS ARRANGED. OPPOSITE EACH OTHER ON AN INSULATOR AND HAVING HELICAL CREEP-PREVENTING RIBS Haakon Forwald, Ludvika, Sweden, assignor to Allmiinna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Filed Oct. 21, 1963, SerlNo. 317,682

Claims priority, application Sweden, Nov. 10, 1962, 12,082/62 3 Claims. (Cl. 200150) The present invention relates to an oil circuit breaker with a number of series-connected breaking gaps arranged in a tube-shaped insulator. The breaking gaps comprise movable contacts electrically connected in pairs carried by a common operating device. Each such pair of movable contacts is arranged to close an interruption path between a corresponding pair of fixed contacts, which are supported by the insulator wall. The invention is characterized in that the breaking gaps composed of such movable and fixed contacts are series-connected by means of electrical connections arranged on the outside of the insulator and that between two consecutive connections or between a connection and an end terminal for the series of breaking gaps an external insulating shield is arranged on the insulator. By means of the invention a simple and compact construction of a breaker is obtained which make it especially suitable as a load interrupter for insulators for high voltages. The exterior insulation shields enable the series breaking gaps to be arranged near to each other in the insulator while providing an adequate creeping distance between two consecutive connections.

An especially compact embodiment of the circuit breaker may be obtained if the insulated shields are placed on the insulator in parallel planes arranged at a predetermined distance from each other and forming inclined angle with the longitudinal axle of the insulator. Insulator porcelain of this type may be manufactured by casting but it might also be feasible to use a turning tool having periodical to and fro movements in the longitudinal direction of the insulator.

In order to improve the extinguishing effect of the different breaking gaps the movable contacts are provided with nozzles passing therethrough and are placed on the operating device which is suitably composed of a casing of insulating material, the oil outside the casing being in communication with its interior through the nozzles in the movable contacts.

The flow of oil through the nozzles is increased during opening by a piston connected to the operating device.

In the event that the movable contact in a contact pair is arranged on the casing-shaped operating device at the same height as the movable contact in a following pair, it is suitable to arrange a longitudinal shield in the casing between the nozzle openings from said movable contacts in order to prevent the gases from corresponding nozzles from immediately meeting each other when the circuit is broken. This might lead to a re-ignition since the nozzles in question have different potentials after a breaking action.

The invention may be understood with reference to accompanying FIGURES 1 and 2 which show two different embodiments of the invention.

In FIGURE 1, 1 indicates the tube-shaped insulator. The insulator is of normal design and provided with shields 2 which lie in planes perpendicular to the longitudinal direction of the insulator. The movable contacts are indicated by 3" and 3", and 4 and 4" respectively. Corresponding fixed contacts are indicated by 5' and 5", and 6 and 6 respectively. The fixed contacts are fixed 3,247,348 Patented Apr. 19, 1966 to the wall by means of bolts 7-10 which pass through the wall of the insulator 1. In the figure the bolts 7 and 10 are connected to end terminals 11 and 12 respectively. The bolt 8 is connected to the bolt 9 by means of a further connection 13. Said connection is shielded from the bolts 7 and 10 of the end contacts by means of the shields 2 running around the insulator.

The movable contacts are arranged on a casing 14 of insulating material and connected together by means of connections 15 and 16. The interior of the casing 14 communicates with the surrounding space by means of the nozzles arranged in the movable contacts and in ad-- dition possibly also by means of one or more small leakage holes in the casing 14. 17 is a piston connected to the casing 14. In the top of the breaker, check valves 18 and 19 are arranged. 20 is a parallel resistance connected so as to ensure even voltage distribution over the different breaking gaps.

During an opening movement the casing 14 is moved downwards, upon which the oil in the space outside the cylinder is actuated by the piston 17 being moved downwards at the same time that the return valves 18 and 19 are closed. The oil flows through the nozzles in the movable contacts into the casing 14 and simultaneously cools the arcs at the ditierent breaking gaps. In order that the oil or gas flow through the nozzle in the contact 4' shall not meet the gas flow from the nozzle in the contact 3" an insulating shield 21 is arranged in the casing 14 between the openings from said nozzles.

In FIGURE 2 an oil circuit breaker is shown of the same general construction as the oil circuit breaker in FIGURE 1. The difference here is that the shields 2 are arranged in planes which form inclined angles to the insulator axle. With this arrangement, the movable contacts belonging to the same pair may be placed at the same height. This in its turn make it possible now to arrange three pairs of movable contacts with corresponding fixed contacts in the same space which in FIG- URE l is only suflicient for two pairs of movable contacts with corresponding fixed contacts.

Finally it should also be noted that when using a relatively large number of breaking gaps the voltage per breaking gap will be low and a fairly reasonable oil pressure is thereby sufficient for extinguishing the arcs formed during a breaking action. This has the effect that, in spite of the piston fixed to the operating device, the mechanical force for operating the breaker is fairly reasonable and can be produced with a small operating device. In the event that the oil breaker is made with a large number of breaking gaps it is further suitable to use an exterior parallel connected switch which is opened before a breaking. Resistances for even distribution of the voltage over each breaking point pair are arranged as shown in the figures and the resistance current may be broken by the series connected isolator with which the oil circuit breaker is intended to cooperate. The oil circuit breaker need not of course be arranged vertically as shown in the figures but may be inclined or lie almost completely horizontally, upon the assumption of course that the upper part of the oil breaker is properly adapted to the oil surface.

I claim:

1. An oil circuit breaker comprising an elongated hollow insulator, an operating member movably mounted in said insulator, and a plurality of breaking gaps therein each having a stationary contact carried by the insulator wall and a movable contact carried by the operating member, said breaking gaps being arranged in series-connected groups, each group including first and second breaking gaps arranged in substantially the same plane transverse to the longitudinal axis of the insulator, said contacts of being electrically connected, an electrical connection on.

the outside of the insulator extending substantially helically between a first stationary contact of each group and a second stationary contact of an adjacent group, said first and second stationary contacts being located at substantially diametrically opposite sides of the insulator, and an external insulating shield projecting outwardly from the insulator between each two outside connections, said shield being substantiallyparallel to said connections. 7 I

'2. An oil circuit breaker according to claim 1, in 15 which the operating member is a tube of insulating material, said movable contacts having nozzle means therein for connecting the exterior of said tube with its interior.

3. An oil circuit breaker according to claim 2; having piston means connected to the operating member to effect a flow of oil through said nozzles into said tube dur- 5 ing movement of the operating member to circuit opening position.

References Cited by the Examiner UNITED STATES PATENTS I 2,098,801 11/1937 Erben 200--l 2,675,505 4/1954 Flurs-cheim et al. 2040- 2,789,186 4/ 1957 Coggeshall 200- KATHLEEN H. CLAFFY, Primary Examiner.

P. E. CRAWFORD, Assistant Examiner. 

1. AN OIL CIRCUIT BREAKER COMPRISING AN ELONGATED HOLLOW INSULATOR, AN OPERATING MEMBER MOVABLY MOUNTED IN SAID INSULATOR, AND A PLURALITY OF BREAKING GAPS THEREIN EACH HAVING A STATIONARY CONTACT CARRIED BY THE INSULATOR WALL AND A MOVABLE CONTACT CARRIED BY THE OPERATING MEMBER, SAID BREAKING GAPS BEING ARRANGED IN SERIES-CONNECTED GROUPS, EACH GROUP INCLUDING FIRST AND SECOND BREAKING GAPS ARRANGED IN SUBSTANTIALLY THE SAME PLANE TRANSVERSE TO THE LONGITUDINAL AXIS OF THE INSULATOR, SAID CONTACTS OF THE FIRST BREAKING GAPS ALL BEING ALIGNED ON ONE SIDE OF THE INSULATOR AND SAID CONTACTS OF THE SECOND BREAKING GAPS ALL BEING ALIGNED ON THE DIAMETRICALLY OPPOSITE SIDE OF THE INSULATOR, THE TWO MOVABLE CONTACTS OF EACH GROUP BEING ELECTRICALLY CONNECTED, AN ELECTRICAL CONNECTION ON THE OUTSIDE OF THE INSULATOR EXTENDING SUBSTANTIALLY HELICALLY BETWEEN A FIRST STATIONARY CONTACT OF EACH GROUP AND A SECOND STATIONARY CONTACT OF AN ADJACENT GROUP, SAID FIRST AND SECOND STATIONARY CONTACTS BEING LOCATED AT SUBSTANTIALLY DIAMETRICALLY OPPOSITE SIDES OF THE INSULATOR, AND AN EXTERNAL INSULATING SHIELD PROJECTING OUTWARDLY FROM THE INSULATOR BETWEEN EACH TWO OUTSIDE CONNECTIONS, SAID SHIELD BEING SUBSTANTIALLY PARALLEL TO SAID CONNECTIONS. 